The invention relates to a configuration and a method for protecting an integrated circuit against over-temperature conditions. Furthermore, the invention relates to an integrated circuit having such a configuration.
During the operation of integrated semiconductor circuits, at least part of the electrical power is converted into heat. Under certain conditionsxe2x80x94for example in the event of overload, short circuit, external heating of the semiconductor chipxe2x80x94this can lead to an undesirable over-temperature condition. In order to detect the over-temperature condition and in order to protect the integrated semiconductor circuits, the latter typically have a temperature protection device. However, the latter must satisfy various requirements.
In circuit configurations having a power switch which is configured for switching loads, such as, for example, a DC motor, an asynchronous motor or the like, a short circuit can occur in the load circuit, through which the power switch or even the load to be switched can be destroyed. In order to protect the power switch, the latter is provided with one or more temperature sensors whose signals are evaluated by an evaluation circuit and which shut down the power switch when a short circuit occurs which results in a great increase in temperature in the power switch. When a predetermined temperature threshold is exceeded, the power switch is shut down and thus protected from destruction. In this case, the temperature sensors, which are typically configured as resistors, diodes or transistor sensors, are preferably integrated in the vicinity of the corresponding hot spot, that is to say in the vicinity of the hottest point in the power switch. The signal of the temperature sensor is then processed by an evaluation circuit in such a way that the power switch is shut down or at the very least power is reduced as soon as the temperature present at the temperature sensor exceeds a predetermined temperature threshold, which is dependent on the respective application and which typically lies above 150xc2x0 C.
Furthermore, temperature sensors are known which are intended to protect the entire integrated circuit from being heated to an excessively great extent. By way of example, the integrated circuit may be heated by an external temperature source, such as, for example, an incandescent lamp driven by the integrated circuit. If the temperature coupled in via the incandescent lamp becomes too high, this can lead to irreversible damage to the integrated circuit, as a result of which the functionality thereof is no longer ensured or it is even destroyed. This applies not only to external heating but also to undesirably great inherent heating. For this purpose, temperature sensors exist which monitor the ambient temperature of the integrated circuit and are preferably disposed in the vicinity of the corresponding hot spot of the integrated circuit. In this case, the so-called xe2x80x9cshutdown/restartxe2x80x9d principle is typically used, according to which the integrated circuit is shut down if the chip temperature detected by a corresponding temperature sensor exceeds a specific value. Once the semiconductor chip has cooled down, for example by 10xc2x0 C., the integrated circuit is switched on again. In the event of a disturbance situation, that is to say if the cause of the over-temperature condition has not been eliminated, the integrated circuit is clocked in accordance with the hysteresis resulting from the shutdown and restart temperature. The constant switching on and off in the case of a disturbance represents a major burden on the integrated circuit which in the medium termxe2x80x94if the disturbance is not rectifiedxe2x80x94will lead undesirably to the failure of the integrated circuit.
In circuit configurations that have a plurality of circuit parts that function independently of one another, as is the case for example with monolithic multi-channel switches, the latter are in each case provided with separate temperature sensors. In the disturbance situation, typically only the defective channel is switched on and off. However, the burden associated with the switching on and off also places a very large burden on the corresponding adjacent channels.
Therefore, two different, partly conflicting requirements result for a temperature sensor. On the one hand, a temperature sensor should have a relatively low threshold for a temperature shutdown, in order that the entire semiconductor chip or the integrated circuit, the housing and further external components are thermally loaded as little as possible in the case of a disturbance. On the other hand, a temperature sensor should have a relatively high threshold for the temperature shutdown in order nevertheless to be functional under certain conditions, for example when an incandescent lamp is switched on or in the event of a momentary, yet not disturbing overload.
The prior art has only disclosed temperature sensors in which the threshold at which a temperature-dictated shutdown of the power switch or of the integrated circuit is affected is adapted in one direction or the other, but does not simultaneously satisfy all the requirements mentioned above.
It is accordingly an object of the invention to provide a circuit configuration with temperature protection and a method for implementing the temperature protection which overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which is better adapted to the respective requirements, and furthermore, the least possible mutual thermal influencing of the individual circuit parts should be possible in so-called multi-channel ICs.
With the foregoing and other objects in view there is provided, in accordance with the invention, a configuration for protecting an integrated circuit against over-temperature conditions. The configuration contains at least one detector device for identifying a disturbance situation regarding the integrated circuit, at least one temperature sensor for detecting a temperature of at least one part of the integrated circuit, and a logic device for ascertaining a disturbance mode derived from the disturbance situation and/or the temperature. The logic device allocates a first temperature switching stage to the temperature sensor in a normal mode and a second, lower temperature switching stage to the temperature sensor in the disturbance mode. The logic device is connected to both the temperature sensor and the detector device.
With the foregoing and other objects in view there is additionally provided, in accordance with the invention, a method for protecting an integrated circuit against over-temperature conditions. The method includes the steps of checking the integrated circuit for a disturbance situation; checking a temperature of at least one part of the integrated circuit; ascertaining an occurrence of a disturbance mode based on at least one of the disturbance situation and the temperature; and allocating a first temperature switching threshold to a temperature sensor in a normal mode and a second, lower temperature switching threshold to the temperature sensor in the disturbance mode.
With the foregoing and other objects in view there is further provided, in accordance with the invention, an integrated circuit. The integrated circuit has a first terminal for a first supply potential, a second terminal for a second supply potential, and a controllable semiconductor switch disposed between the first terminal and the second terminal. The controllable semiconductor switch has a load path and a control terminal. A load is connected in series with the load path of the controllable semiconductor switch. A drive circuit is coupled to and drives the control terminal of the controllable semiconductor switch. A configuration for protection against over-temperature conditions as described above is provided.
The temperature sensor according to the invention is distinguished by an over-temperature protection configuration configured in at least two stages. The circuit parts that are operated in the normal mode and have relatively high temperature values on account of a momentary overload or a momentary short circuit are allocated a first temperature switching stage. Circuit parts which exhibit a disturbance situation and which, because of this, are heated up or heat up the entire semiconductor chip to an excessively great extent are allocated a second temperature switching stage, which is lower than the first temperature switching stage. A determining factor for the temperature-dictated shutdown of the entire circuit is in each case the second, lower temperature switching stage, without however precluding a momentary occurrence of a higher temperature that in each case lies below the first temperature switching stage. As a result, the temperature protection for the entire integrated semiconductor circuit is advantageously ensured and, moreover, it is ensured that a momentary cross-talk of the temperature does not lead undesirably to the switching off of individual circuit parts or of the entire circuit configuration.
The two temperature switching stages can advantageously be optimally adapted to the respective requirements, with the result that, in contrast to known temperature sensors, these do not have to be optimized in one direction or the other.
Each temperature stage advantageously has a shutdown value and a restart value, which can thus both operate according to the shutdown/restart principle.
Furthermore, the temperature sensor according to the invention with a temperature switching stage configured in two stages also prevents the thermal cross-talk in multi-channel circuits, since a temperature threshold defined in a respectively dedicated manner can be allocated for each individual channel and thus for the corresponding circuit parts. The criteria evaluated for the changeover are typically logic signals that may be representative of the respective state of the individual circuit parts or of the entire system.
In accordance with an added feature of the invention, the first temperature switching stage and the second, lower temperature switching stage are two temperature switching thresholds configured as a switching hysteresis in which the first temperature switching stage has a first shutdown temperature threshold and a first, lower switch-on temperature threshold and in which the second, lower temperature switching stage has a second shutdown temperature threshold and a second, lower switch-on temperature threshold.
In accordance with an added feature of the invention, the at least one temperature sensor is one of a plurality of temperature sensors, and a multiplicity of channels are provided for monitoring a temperature of an identical number of channels of the integrated circuit. Each of the channels of the configuration has one of the temperature sensors, and the temperature sensor in each case supplies an analog signal as a measure of the temperature of a circuit part to be monitored.
In accordance with an additional feature of the invention, the detector device is a short-circuit identification circuit supplying a signal as a measure of the disturbance situation in a form of a short circuit in a load circuitxe2x80x94to be monitoredxe2x80x94of the integrated circuit.
In accordance with another feature of the invention, the detector device has a device for identifying an overload condition, and supplies a signal as a measure of the disturbance situation that is in a form of a momentary overloadxe2x80x94caused by a capacitive loadxe2x80x94in a load circuitxe2x80x94to be monitoredxe2x80x94of the integrated circuit.
In accordance with a further feature of the invention, the at least one detector device is one of a plurality of detector devices each functioning as a short-circuit identification circuit, and each of the channels of the configuration has one of the detector devices.
In accordance with a further added feature of the invention, the at least one detector device is one of a plurality of detector devices each functioning as a device for identifying an overload condition, and each of the channels of the configuration has one of the detector devices.
In accordance with a further additional feature of the invention, the detector devices also function as devices for identifying an overload condition and/or as a short-circuit identification circuits.
In accordance with another further feature of the invention, the detector device has a further temperature sensor for monitoring a temperature of at least one of the integrated circuit entirely and an ambient temperature around the integrated circuit.
In accordance with a concomitant feature of the invention, the further temperature sensor is to be disposed on a lead frame and supplies a signal as a measure of the disturbance situation, the signal being dependent on a lead frame temperature.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit configuration with temperature protection and a method for implementing the temperature protection, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.